It's not too hard, just a lot of effort on details. First there's the parsing, and creating related Ast node types which is pretty easy. The big thing is all present internal analysis assumes the entire state of the model is available for static analysis, that will have to be bypassed. (Not allowing <= assignments would simplify.) Then the actual implementation which can yes be a map, though the key type needs to allow arbitrary width numbers. This needs to be implemented (as most things are) in both verilator for static analysis and in the runtime. Finally there's how to waveform trace something like this.

If you only have a few, you can easily make a dpi function to do your lookup or faster something like this instead (untested): Note that using `systemc stuff disables some optimizations.